Tailings Management Areas

Wismut GmbH has responsibility for the rehabilitation of four tailings management areas: the Helmsdorf and Dänkritz 1 facilities near the town of Zwickau as well as the Culmitzsch and Trünzig facilities at the Seelingstädt site. Together they cover an area of more than 570 hectares and contain fine-grained tailings from the processing of uranium ores. Rehabilitation of the tailings management areas is one of the largest challenges of the Wismut project.

During the first years after the mills shut down, emphasis at all sites was placed on immediate remediation efforts to protect workers and the general public against harmful effects. To this end, exposed beach areas were covered with mineral soil to reduce wind-blown dispersal of radioactive dust. Seepage collection systems were extended and new systems were constructed to protect surface waters and aquifers. While immediate hazards were mitigated, studies investigated various remedial options for achieving long-term stabilisation of the tailings ponds. As a result, dry in-situ stabilisation was selected as the most cost-efficient option. It involves rehabilitation in place, removal of supernatant water, stabilisation of fine-grained residues using geotechnical means, and construction of a final cover of different layers of mineral materials. This general engineering approach is being applied at all four sites.

In recent years, stabilisation of tailings ponds has made good progress.

At the Helmsdorf and Culmitzsch facilities, pond water is not yet completely removed while construction of an interim cover is under way and the final contour is partially in place. The engineering approach to interim cover construction had to be modified at both sites. Given the complex geotechnical conditions prevailing in the centre of both ponds, very fine slimes have to be stabilised prior to the removal of pond water. To this end, several thin layers of free flowing materials (waste rock, gravel/sand, respectively) are dumped from a hopper barge onto the low bearing bottom in an operation known as subaqueous dumping. This technology known as subaqueous cover placement was implemented from 2002 through 2003, following successful test placements at the Helmsdorf tailings site in 1998. A tug barge unit was operated on basin A of the Culmitzsch tailings site since spring 2004 and the cover placement operation was terminated before the end of that year.

Currently, and for a couple of years to come, focus is on recontouring the tailings sites and on placing a final cover. In a further step trails and ditches to catch and control surface water run-off will be constructed. Finally, the constructed landscape features will be seeded and planted. Remediation work at the Helmsdorf and Trünzig sites is scheduled to be accomplished in the medium-term while it will take longest at the Culmitzsch site. A number of long-term tasks will have to be accomplished in order to ensure continued remediation performance.